The Nasdaq 100′s close below its 50-day moving average on Thursday doesn’t necessarily warn of immediate, sharp declines, but it does hint that other major market indexes are likely to eventually do the same.

That implies near-term bounces in the S&P 500 should remain contained by nearby resistance.

Technical analysts use moving averages to help smooth out daily fluctuations so they can have a clearer view of the underlying trend. One of the more widely viewed is the 50-day moving average line, which many use to track the short-term trend. When an index crosses below the 50-day line after a relatively long period above, it suggests the short-term trend has started shifting to the downside.

Now that Dell Inc. looks set to go private, Netflix Inc. is next in line for inclusion in the Nasdaq-100 Index.

The index is made up of the largest 100 non-financial companies listed on the tech-heavy exchange. Nasdaq has an index of the securities that are next-eligible for inclusion in the Nasdaq-100, called the Nasdaq-Q50 Index. Netflix, with a $9.7 billion market capitalization, is the biggest in that index, according to exchange data.

The Nasdaq-100 Index is the base for the widely watched PowerShares QQQ exchange-traded fund, which has $32 billion in assets.

Facebook Inc.’s move to the Nasdaq 100 on Wednesday is expected to have a relatively minor impact on the tech-heavy index.

Facebook is expected to hold a 1.02% weighting in the Nasdaq 100, which would make it the 23rd biggest component in the index, according to data provider Markit. By comparison, the five biggest stocks have weightings of 3.7% and greater.

Apple Inc. is, by far, the largest component in the index. It currently has weighting of 17%, which Markit estimates will drop to 16.5% after Facebook joins the club.

Microsoft Corp is second at 7.5% and Google Inc. is third at about 6%. Oracle Corp. and Amazon.com Inc. round out the top five, with weightings of 5.2% and 3.7%, respectively.

That means the top five components make up nearly 40% of the index, according to Markit.

Apple has a thing or two to do with the bullish sentiment surrounding the Nasdaq 100.

Investors appear to be a little too bullish on the Nasdaq 100, following the index’s rally to the highest level in a decade, as sentiment readings and a classic reversal signal suggest a significant pullback may have begun.

The PowerShares QQQ (QQQ) is the exchange traded fund that tracks the Nasdaq 100. The number of triple-Q shares outstanding can fluctuate on a daily basis, depending on investor interest. For example, the more investors buy the ETF, the more shares are issued as PowerShares attempts to keep share price in line with the net asset value.

Tom McClellan, publisher of the McClellan Market Report, noted that the number of current shares outstanding is at the highest level since 2006, and more than 8% above the 2011 highs. Meanwhile, the triple-Qs high last week was less than 2% above the 2011 high.

McClellan said this indicates the current level of interest in owning the triple-Qs is well ahead of the corresponding highs in 2011, suggesting investors may have become a bit “overzealous.”

In addition, he said the number of shares outstanding has climbed above a line he’s drawn that is one standard deviation above the 50-day moving average.

“That means that traders have been drawn into owning this ETF to a degree even greater than what the raw price advance itself would suggest should have happened,” McClellan said. “That overly bullish sentiment condition begs for at least a short-term pullback, to reintroduce people to the idea that stock prices actually ‘can’ go down.”

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